Delaying layer 2 frame transmission

ABSTRACT

Datalink frames or networking packets contain protocol information in the header and optionally in the trailer of a frame or a packet. We are proposing a method in which part of or all of the protocol information corresponding to a frame or a packet is transmitted separately in another datalink frame. The “Separately Transmitted Protocol Information” is referred to as STPI. The STPI contains enough protocol information to identify the next hop node or port. STPI can be used avoid network congestion and improve link efficiency. Preferably, there will be one datalink frame or network packet corresponding to each STPI, containing the data and the rest of the protocol information and this frame/packet is referred to as DFoNP. The creation of STPI and DFoNP is done by the originator of the frame or packet such as an operating system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 17/062,594, filed on Oct. 4, 2020, entitled “Data Link Frame Reordering”, now U.S. Pat. No. 11,398,985, issued on Jul. 26, 2022, which is a continuation of U.S. application Ser. No. 16/132,427, filed on Sep. 16, 2018, entitled “Network Congestion and Packet Reordering”, now U.S. Pat. No. 10,841,227, issued on Nov. 17, 2020 which is a continuation of U.S. application Ser. No. 15/268,729, filed on Sep. 19, 2016, entitled “Networking using PCI Express”, now U.S. Pat. No. 10,110,498, issued on Oct. 23, 2018, which is a divisional application of U.S. application Ser. No. 14/120,845, filed on Jul. 1, 2014, entitled “Method for Congestion Avoidance”, now U.S. Pat. No. 9,479,442, issued on Oct. 25, 2016, which is a continuation of U.S. application Ser. No. 13/385,155, filed on Feb. 6, 2012, entitled “Method for Identifying Next Hop”, now U.S. Pat. No. 8,811,400 issued on Aug. 19, 2014, which is a continuation of U.S. application Ser. No. 11/505,788, filed on Aug. 18, 2006, entitled “Creation and Transmission of Part of Protocol Information Corresponding to Network Packets or Datalink Frames Separately”, now U.S. Pat. No. 8,139,574 issued on Mar. 20, 2012, all of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to efficient transfer of datalink frame or network packets in a “custom” network. The network is “custom” as all switches and end nodes need to create or process datalink frames or data packets of special formats.

The OSI, or Open System Interconnection, model defines a networking framework for implementing protocols in seven layers. Most networking protocols do not implement all seven layers, but only a subset of layers. For example, TCP and IP protocol corresponds to layers 4 (TCP) and 3 (IP) respectively. Network packets contain protocol layer information corresponding to the packet. For example, a TCP/IP packet contains a header with both TCP and IP information corresponding to the packet.

The physical layer (layer 1) specifies how bits stream is created on a network medium and physical and electrical characteristics of the medium. The datalink layer (layer 2) specifies framing, addressing and frame level error detection. For outgoing packets to the network, the datalink layer receives network packets from networking layer (layer 3) and creates datalink frames by adding datalink (layer 2) protocol information and passes the frame to the physical layer. For incoming packets from network, datalink layer receives datalink frames from physical layer (layer 1), removes the datalink (layer 2) protocol information and passes network packet to the networking layer. The network layer (layer 3) specifies network address and protocols for end to end delivery of packets.

Network packets contain protocol layer information corresponding to the packet. FIG. 1A illustrates a network packet containing 01001 layer 1, 01002 layer 2, 01003 layer 3, 01004 layer 4 headers, 01005 Data and 01008 layer 1, 01007 layer 2, 01006 layer 3 trailers. FIG. 1B illustrates a network packet with 01011 layer 1, 01012 layer 2 (data link), 01013 layer 3 (networking) and 01014 layer 4 (transport) headers and 01017 layer 1 and 01016 layer 2 trailers and 01015 Data. For each layer, the corresponding header and trailer (if present) together contain all the protocol information required to send the packet/frame to the consumer of the data in a remote node.

For example, headers/trailers corresponding to a TCP/IP packet in a 10BaseT Ethernet LAN are:

-   -   i) Physical layer header contains Start-of-Stream Delimiter     -   ii) Data link layer header contains Preamble, Start-of-Frame         Delimiter, Ethernet Addresses, Length/Type Field etc.     -   iii) IP header contains Version, Length, IP Address etc.     -   iv) TCP header contains Port Numbers, Window, Flags etc.     -   v) Datalink layer trailer contains 32 bit FCS     -   vi) Physical layer trailer contains End-of-Stream Delimiter.

When parts of networks get congested and end nodes continue transmitting packets to congested parts of a networks, more and more switches can get congested. This can lead to switches dropping large number of packets, nodes retransmitting the dropped or lost packets and network slowing down.

U.S. Pat. No. 6,917,620 specifies a method and apparatus for a switch that separates the data portion and the header portion. This method has a disadvantage that overhead and logic for separating the data portion and the header portion and then combining the header portion and the data portion before transmission is required. This method also can not consolidate headers from more than one packet for transmission to the next node or delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.

According to claim (1)(c) of U.S. Pat. No. 5,140,582, the header portion of a packet is decoded prior to the receipt of full packet to determine the destination node. This invention can help with faster processing of the packet within a switch. This method can not consolidate headers from more than one packet for transmission to the next node or delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.

U.S. Pat. No. 6,032,190 specifies an apparatus and method of separating the header portion of an incoming packet and keeping the header portion in a set of registers and combining the header portion with the data portion before transmitting the packet. This method has a disadvantage that overhead and logic for separating the data portion and the header portion is required. This method can not consolidate headers from more than one packet for transmission to the next-node or delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.

U.S. Pat. No. 6,408,001 improves transport efficiency by identifying plurality of packets having common destination node, transmitting at least one control message, assigning label to these packets and removing part or all of header. This method has a disadvantage that switches need to identify messages with common destination node and additional logic to remove header and add label. This method can not delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.

BRIEF SUMMARY OF THE INVENTION

It is the object of the present invention to create and transmit part of protocol information separately from the Datalink Frame or Network Packet (DFoNP) containing data. The Separately Transmitted Protocol Information is referred to as STPI. Network congestion can be reduced or avoided using STPI.

According to the invention, there should be at least one DFoNP which contains the data and rest of the protocol information not contained in STPI, corresponding to each STPI. Preferably, there will be only one DFoNP corresponding to each STPI. The STPI and DFoNP together contain all the protocol information required to send the packet/frame to the consumer of the data in a remote node.

The creation of STPI and DFoNP is done by the originator of the frame or packet such as an operating system in an end node. The format (contents and location of each information in a frame or packet) of the frame or packet containing STPI and DFoNP should be recognized by the final destination of the frame or packet. The format of STPI and DFoNP should also be recognized by switches in the network. So preferably, all STPIs and DFoNP in a given network should be of fixed formats.

Preferably, one or more STPIs are transmitted in a datalink frame or a network packet. The datalink frame containing STPIs is referred to as STPI Frame. The network packet containing STPIs is referred to as STPI packet. The switches in this case should be capable of extracting each STPI in an incoming STPI Frame or STPI packet and forwarding it to the next node in a different STPI Frame or STPI Packet. The switches can add each STPI from an incoming STPI Frame or STPI Packet into an STPI Frame or STPI Packet it creates. Preferably, the layer 2 address in the datalink frame containing multiple STPIs will be the next hop node address.

Optionally, STPI Frame or STPI Packet contains number of STPIs or length of the STPI frame. Optionally, STPI Frame or STPI Packet contains the offset or position of STPIs in the STPI frame—this is required only if STPIs supported by the network are not of fixed length.

Optionally, STPI Frame or STPI Packet does not contain the number of STPIs and switches in the network are capable of identifying the number of STPIs from length of the frame as they are of fixed length.

Preferably, some protocol information contained in STPI may not be contained in the corresponding DFoNP. But protocol information contained in STPI and the corresponding DFoNP need not be mutually exclusive. In this method, the switches obtain both STPI and the corresponding DFoNP before the STPI and the corresponding DFoNP are forwarded. Optionally, STPI need not be forwarded to end node if sufficient protocol information is contained in the corresponding DFoNP.

The proposed invention can be employed for data, control and/or RDMA packets in a network.

The proposed method allows switches to read the more than one STPI, and then delay obtaining the corresponding DFoNP. The DFoNP may be read or forwarded in a different order compared to the order in which STPI are read or forwarded. This method allows switches to optimize resources and packet/frame forwarding efficiency.

STPI contain temporary information such as current node or port number of the node containing the corresponding DFoNP. STPI also contains an address of a buffer containing the corresponding DFoNP or an offset in a buffer where the corresponding DFoNP is stored or an index of the corresponding DFoNP in an array. These information help in associating STPI to the corresponding DFoNP. The exact information contained in STPI whether it is an address or an offset or an index or a combination of these is implementation specific.

Optionally, STPI may contain originating node identifier and a sequence number. Such information can help in reporting errors when STPI or corresponding DFoNP are corrupted or lost.

Optionally, STPI may contain other vendor specific or DFoNP related miscellaneous information.

Optionally, DFoNP may contain some information that help in associating itself with corresponding STPI, such as originating node identifier and a sequence number. Preferably, DFoNP sequence number is same as the sequence number of the corresponding STPI.

Optionally, DFoNP may contain other vendor specific miscellaneous information.

The originating node creating an STPI by creating and initializing one or more data structures. Preferably, there is only one data structure containing STPI.

A switch receiving both frame containing STPI and the DFoNP before forwarding a frame containing STPI or DFoNP to the next switch or node.

Preferably, a switch receiving frame containing STPI before reading the corresponding DFoNP.

A switch can delay transmitting or reading DFoNP after the corresponding STPI is transmitted or received, allowing the switch to optimize its resource usage and improve efficiency.

A switch can read DFoNPs corresponding to a switch port with minimum outbound traffic, ahead of other DFoNPs, thereby improving link efficiency.

The switch modifying temporary information in STPI such as node number or port number corresponding to the node containing corresponding DFoNP and buffer pointer or index or offset for the corresponding DFoNP, when the DFoNP is transmitted to another node.

If the DFoNP and STPI is forwarded to another subnet, layer 2 information in STPI and DFoNP should be updated to be compatible with the subnet to which it is forwarded (for example, in an IP network when a packet moves from Ethernet to ATM, layer 2 protocol information will have to be modified to be made compatible with ATM network).

If STPI contains a multicast or broadcast destination address, the switch transmitting both the DFoNPs and the STPI to all next hop nodes identified by the address.

A switch can delay reading or forwarding the DFoNP after the corresponding STPI is received or forwarded, and vice versa.

A switch may or may not receive or transmit DFoNPs in the same order as the corresponding STPIs are received or transmitted from a switch port.

Optionally, a switch may receive or transmit one or more DFoNP in one frame.

For networks that support layer 5/6/7 (example OSI networks), STPI optionally containing part of or all of layer 5/6/7 information. Preferably, no layer 5/6/7 information may be contained in STPI.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A illustrates a network packet containing layer 1, layer 2, layer 3, layer 4 headers, Data and layer 1, layer 2, layer 3 trailers.

FIG. 1B illustrates a network packet with layer 1, layer 2 (data link), layer 3 (networking) and layer 4 (transport) headers and layer 1 and layer 2 trailers and Data.

FIG. 2A illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2B illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2C illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2D illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2E illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2F illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2G illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2H illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2I illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2J illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2K illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2L illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2M illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 2N illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs.

FIG. 3A illustrates Switch/Node A containing an STPI and the corresponding DFoNP to be transmitted to the Switch/Node B.

FIG. 3B illustrates the Switch/Node A sending an STPI frame containing the STPI.

FIG. 3C illustrates the Switch/Node B deciding to fetch the DFoNP corresponding to the STPI and sending Read-DFoNP Frame to the Switch/Node A containing the Read-DFoNP request for the DFoNP.

FIG. 3D illustrates the Switch/Node A responding to the Read-DFoNP request for the DFoNP by sending the DFoNP.

FIG. 3E illustrates the STPI being updated with the identifier of the Switch/Node B and the location of the DFoNP in the Switch/Node B.

FIG. 4A illustrates Switch/Node A containing an STPI and the corresponding DFoNP to be transmitted to the Destination Node B.

FIG. 4B illustrates the Switch/Node A transmitting an STPI Frame containing the STPI to the Switch/Node B.

FIG. 4C illustrates the Switch/Node A transmitting the DFoNP to the Switch/Node B.

FIG. 4D illustrates the Switch/Node B updating the STPI with the location of the DFoNP in the Switch/Node B.

FIG. 5A illustrates Switch/Node A containing an STPI and the corresponding DFoNP to be transmitted to the Switch/Node B.

FIG. 5B illustrates Switch/Node A transmitting a frame containing the STPI to the Switch/Node B.

FIG. 5C illustrates the Switch/Node B deciding to fetch the DFoNP corresponding to the STPI and sending Read-DFoNP Frame to the Switch/Node A containing DFoNP request for the DFoNP.

FIG. 5D illustrates the Switch/Node A responding to the Read-DFoNP request by transmitting the DFoNP.

FIG. 5E illustrates the STPI being updated with identifier of Switch/Node B and the location of the corresponding DFoNP in the Switch/Node B.

FIG. 6A illustrates Switch/Node A containing an STPI and the corresponding DFoNP to be transmitted to the Switch/Node B.

FIG. 6B illustrates the Switch/Node A responding by sending an STPI frame containing all STPIs to be transmitted to the Switch/Node B.

FIG. 6C illustrates the Switch/Node A transmitting the DFoNP corresponding to the STPI to the Switch/Node B.

FIG. 6D illustrates the STPI being updated with identifier of the Switch/Node B and the location of the corresponding DFoNP in the Switch/Node B.

FIG. 7A illustrates Switch/Node A containing an STPI and the corresponding DFoNP to be transmitted to the Destination End Node B.

FIG. 7B illustrates Switch/Node A transmitting the DFoNP to the Destination End Node B and updating the STPI with the location (DMA address) of the DFoNP in the Destination End Node B.

FIG. 7C illustrates Switch/Node A transmitting the STPI in an STPI frame to the Destination End Node B.

FIG. 7D illustrates that both STPI and DFoNP are received by End Node B.

FIG. 8A illustrates a Read-STPI frame with Frame Type “Read-STPI” and “Number of STPIs” set to 3.

FIG. 8B illustrates a Read-STPI frame in a network where explicit frame type specification is not required.

FIG. 8C illustrates a Read-STPI frame in a network without layer 1 headers or trailers.

FIG. 8D illustrates a Read-STPI frame in a network without layer 1 headers or trailers.

FIG. 9A illustrates a Read-DFoNP frame with Frame Type“Read-DFoNP” and “Number of Read-DFoNP requests” set to 2.

FIG. 9B illustrates a Read-DFoNP frame in a network where explicit frame type specification is not required.

FIG. 9C illustrates Read-DFoNP frame in a network without layer 1 headers or trailers.

FIG. 9D illustrates a Read-DFoNP frame in a network without layer 1 headers or trailers.

FIG. 10A illustrates a Number-of-STPIs frame with Frame Type“Number-of-STPIs” and “Number of STPIs” set to 3.

FIG. 10B illustrates Number-of-STPIs frame in a network where explicit frame type specification is not required.

FIG. 10C illustrates Number-of-STPIs frame in a network without layer 1 headers or trailers.

FIG. 10D illustrates a Number-of-STPIs frame in a network without layer 1 headers or trailers.

FIG. 11A illustrates an example of DFoNP and STPI frames which can be used with Ethernet.

FIG. 11B illustrates Read-DFoNP frame which can be used with Ethernet.

FIG. 12A illustrates format of PCI Express Read Completion containing DFoNP, from a root bridge in response to a Memory Read request from a switch.

FIG. 12B illustrates format of PCI Express Read Completion containing STPIs, from a root bridge in response to a Memory Read request from a switch.

FIG. 12C illustrates a PCI Express Memory Write transaction containing DFoNP, from a switch to a root bridge.

FIG. 12D illustrates a PCI Express Memory Write transaction containing STPIs, from a switch to a root bridge.

FIG. 13A illustrates a frame containing both Number-of-STPIs message and Read-DFoNP requests.

FIG. 13B illustrates a frame containing both Read-STPI request and Read-DFoNP requests.

FIG. 14A illustrates Switch A has 3 DFoNPs to be transmitted to Switch B.

FIG. 14B illustrates the switch identifying that STPI[1] and STPI[2] received are for node D and adding STPI[1] and STPI[2] to the queue for the node D.

DETAILED DESCRIPTION OF THE INVENTION

There are a very large number of design options with network component designers with respect to the format of DFoNP, STPI and STPI frame/packet. FIG. 2A, FIG. 2B, FIG. 2C, FIG. 2D, FIG. 2E, FIG. 2F, FIG. 2G, FIG. 2H, FIG. 2I, FIG. 2J, FIG. 2K, FIG. 2L, FIG. 2M and FIG. 2N illustrate some examples of different formats in which the STPI and the corresponding DFoNP can be created adhering to this invention. The layer 2, layer 3, and layer 4 information that may be present in the DFoNP and STPI may or may not be mutually exclusive and is dependent on specific format or formats of STPI and DFoNP supported by switches and endnodes. Each network will employ only few STPI/DFoNP formats (preferably, as few as 1-3), one each for a subtype of a packet or a frame. Preferably, a network may employ only one format for STPI and one format for DFoNP to reduce complexity in switches and endnodes. STPI should have enough information for the switch to find the port for the next hop.

-   -   i) FIG. 2A illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. All         layer 2 02021 02024 (including Destination Node Address used for         routing), layer 3 02022 and layer 4 02023 information are in         STPI and the DFoNP contains no layer 3 and 4 information. DFoNP         contains minimal layer 2 02001 02004 information mandated by         datalink layer (an example of optional layer 2 information is         the VLAN tag in Ethernet). Frame Type in the frame gives the         type of frame, DFoNP 02002, STPI 02012, etc. All data 02003 are         in DFoNP. Three STPIs 02013 are sent in a STPI Frame. The         destination address 02011 of the STPI Frame is the next hop         switch or node address. In this example, 3rd STPI 02014 in the         STPI Frame corresponds to the DFoNP shown. The STPI contains the         length 02026 of the corresponding DFoNP and the current node         number 02025 and current buffer address 02026 containing the         corresponding DFoNP. When the DFoNP is transmitted to the next         node the node number 02025 and buffer address 02026 in the         corresponding STPI are updated.     -   ii) FIG. 2B illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. The         frames in this network do not have layer 2 trailer. All layer 2         02051 (includes destination node address for routing), RDMA         address 02051 for STPI in the destination node, RDMA address         02054 for DFoNP in the destination node, layer 3 02052 and layer         4 02053 information are in STPI. The DFoNP contains no layer 3         and 4 information. In this network, layer 2 02031 02041 contains         frame type and hence, no additional field for frame type is         present. DFoNP contains layer 2 header 02031 with next hop node         address. STPI contains the node number 02055 and an index 02056         to the array containing the corresponding DFoNP. When DFoNP is         transmitted to the next node, the node number 02055 and the         index 02056 in the corresponding STPI are updated. STPI also         contains Source Node Number 02057 (the node number of the node         which created the STPI) and STPI sequence number 02058. The STPI         02042 02043 is the only STPI in the STPI Frame.     -   iii) FIG. 2C illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. All         layer 3 02081 and layer 4 02082 information are in STPI and the         DFoNP contains all 02061 layer 2 information. In this network,         switches use 02081 layer 3 address to find next hop port. So         02071 layer 2 of STPI Frame does not have next hop node address.         Frame Type in the frame gives the type of frame, DFoNP 02062,         STPI 02072, etc. There are 2 STPIs 02073 in the STPI Packet and         the first STPI 02074 corresponds to DFoNP. STPI contains the         DFoNP Current Node Port Number 02083 corresponding to the node         containing DFoNP and an offset 02084 in a buffer to the current         location of the corresponding DFoNP. The port number 02083 is         the port number on the switch containing STPI. When DFoNP is         transmitted to the next node, the port number 02083 and offset         02084 in the corresponding STPI are updated. The port number         02083 is also updated-when STPI is transmitted to the next node.         STPI also contains Source Node Number 02085 and a sequence         number 02086.     -   iv) FIG. 2D illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. STPI         contains layer 3 02112, layer 4 02113, and part of layer 2 02111         protocol information (including route to the destination), RDMA         address 02111 for STPI in the destination node. DFoNP contains         data 02093, part of layer 2 protocol information 02091 02096 and         RDMA address 02091 for the DFoNP in the destination node. STPI         contains 02115 DFoNP length and the port number 02114 and the         buffer address 02115 to the location of the corresponding to         DFoNP. When DFoNP is transmitted to the next node, the port         number 02114 is reset (as DFoNP is in the same node) and buffer         address 02115 in the corresponding STPI are updated. DFoNP Port         number 02114 is also updated when STPI is transmitted to the         next node. Both STPI and DFoNP contains originating node number         02116 02094 and STPI sequence number 02117 02095. The address in         the datalink header 02101 of the STPI Frame is the final         destination node address in the subnet indicating all STPIs in         the STPI Frame are to the same final destination and switching         can be done using STPI Frame address. Frame Type in the frame         gives the type of frame, DFoNP 02092, STPI 02102, etc. STPI         Frame does not contain the number of STPIs as STPIs are of fixed         length and the number of STPIs can be derived from the length of         STPI frame. The first STPI 02103 in the frame corresponds to the         DFoNP shown.     -   v) FIG. 2E illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. STPI         contains part of 02143 layer 2 (Layer 2 in STPI contains         destination address used for routing), RDMA address 02143 for         STPI in the destination node, 02144 part of layer 3 information         and all of 02145 layer 4 information. The DFoNP contains 02121         layer 2 protocol information, RDMA address 02121 for DFoNP in         the destination node and 02123 part of layer 3 information.         Frame Type in the frame gives the type of frame, DFoNP 02122,         STPI 02132, etc. STPI corresponding to the DFoNP shown is the         first STPI 02133 in the STPI Frame. STPI contains the current         node number 02146 and index 02147 to the location of the         corresponding to DFoNP. When DFoNP is transmitted to the next         node, the node number 02146 and index 02147 in the corresponding         STPI are updated. STPI also contains Source Node Number 02141,         STPI Sequence Number 02142 and miscellaneous 02148 information.         The layer 2 header 02131 of the STPI frame contains next hop         node address.     -   vi) FIG. 2F illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. The         network medium does not support layer 1 header or trailer. STPI         contains part of layer 2 02173 (including destination node         identifier used for routing) and part of layer 3 02174 protocol         information. DFoNP contains layers 2 02151, part of layer 3         02153 and all of layer 4 02154 protocol information. STPI         contains the buffer address 02175 and an index 02175 in the         buffer to the location of the corresponding to DFoNP. When DFoNP         is transmitted to the next node, buffer address 02175 and offset         02175 in the corresponding STPI are updated. STPI also contains         Source Node Number 02171, STPI sequence number 02172 and         miscellaneous 02176 information. Frame Type in the frame gives         the type of frame, DFoNP 02152, STPI 02162, etc. The STPI Frame         contains length 02163 of STPIs and since STPIs of this network         are of fixed length, the position of the STPIs in the frame can         be determined by the switch. Expanded view of the second STPI         02164 in the STPI frame is shown. The layer 2 header 02161 of         the STPI frame contains next hop node address.     -   vii) FIG. 2G illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. The         network medium does not support layer 1 header or trailer. STPI         contains part of layer 2 02203 (including destination node         address for routing), part of layer 3 02204 and part of layer 4         02202 protocol information. DFoNP contains layer 2 02181, part         of layer 3 02183 and part of layer 4 02184 protocol information.         STPI contains the current node number 02205, an index to a         buffer 02206 and an offset 02206 in the buffer to the location         of the corresponding DFoNP. When DFoNP is transmitted to the         next node, the node number 02205, the index 02206 and the offset         02206 in the corresponding STPI are updated. STPI also contains         the Source Node Number 02201 and miscellaneous 02207         information. Frame Type in the frame gives the type of frame,         DFoNP 02182, STPI 02192, etc. The STPI Frame contains length         02193 of STPIs and since STPIs of this example are of fixed         length, the position of the STPIs in the frame can be determined         by the switch. Expanded view of the second STPI 02194 in the         frame is shown. The layer 2 header 02191 of the STPI frame         contains next hop node address.     -   viii) FIG. 2H illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. STPI         contains part of layer 2 02233 (including destination node         address for routing) and all of layer 3 02234 protocol         information. The DFoNP contains layer 2 02211 and layer 4 02213         protocol information. STPI contains the length 02235 of the         corresponding DFoNP and the current node identifier 02235,         buffer address 02236 and an offset 02236 in a buffer to the         location of the corresponding DFoNP. When DFoNP is transmitted         to the next node, the Current Node identifier 02235, buffer         address 02236 and the offset 02236 in the corresponding STPI are         updated. STPI also contains Source Node Number 02231 and STPI         Sequence Number 02232. Frame Type in the frame gives the type of         frame, DFoNP 02212, STPI 02222, etc. The STPI Frame in this         example is allowed to have only one STPI 02223. The layer 2         header 02221 of the STPI frame contains next hop node address.         Expanded view of the STPI is shown.     -   ix) FIG. 2I illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. The         network supports protocol layers 5, 6 and 7 in addition to lower         layers. STPI contains 02263 layer 2 and 02264 layer 3         information. The DFoNP contains minimal layer 2 02241 protocol         information allowed by the datalink layer, layer 4, layer 5,         layer 6, and layer 7 02243 protocol information. STPI contains         the current node number 02265, a buffer address 02266 in the         node and an offset 02266 in the buffer to the location of the         corresponding DFoNP. When DFoNP is transmitted to the next node,         the node number 02265, the buffer address 02266 and the offset         02266 in the corresponding STPI are updated. STPI also contains         Source Node Number 02261 and STPI sequence number 02262. Frame         Type in the frame gives the type of frame, DFoNP 02242, STPI         02252, etc. The STPI Frame in this example is allowed to have         only one STPI 02253 and 02251 layer 2 of the STPI frame contains         address of the destination node in the subnet which is used for         routing the STPI frame. Expanded view of the STPI is shown.     -   x) FIG. 2J illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. STPI         contains layer 2 02293 protocol information (including         destination node address for routing). The DFoNP contains 02271         part of layer 2 and all of layer 3 and layer 4 02273 protocol         information. Frame Type in the frame gives the type of frame,         DFoNP 02272, STPI 02282, etc. The STPI[1] 02284 is the only STPI         02283 in the STPI Frame. STPI contains the current node number         02294 and the buffer address 02295 in the node to the location         of the corresponding DFoNP. When DFoNP is transmitted to the         next node, the node number 02294 and the buffer address 02295 in         the corresponding STPI are updated. STPI also contains Source         Node Number 02291 and STPI Sequence Number 02292. DFoNP contains         Source Node Number 02274 and a DFoNP sequence number 02275 which         is different from STPI sequence number. The layer 2 header 02281         of the STPI frame contains next hop node address. Expanded view         of the STPI[1] is shown.     -   xi) FIG. 2K illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. STPI         contains layer 2 02323 information (including destination node         address for routing). The DFoNP contains minimal layer 2 02301         mandated by datalink layer of the subnetwork and all of layer 3         and 4 02302 information. The DFoNP contains control data 02303         such as requests to open a file in addition to data 02303. In         this network, layer 2 02301 02311 protocol information contains         frame type and hence, no additional field for frame type is         present. The STPI[1] 02313 is the only STPI 02312 in the STPI         Frame. STPI contains the length 02324 of the corresponding DFoNP         and the node number 02324 and the buffer address 02325 in the         node to the location of the corresponding to DFoNP. When DFoNP         is transmitted to the next node, the node number 02324 and         buffer address 02325 in STPI are updated. STPI also contains the         Source Node Number 02321 and STPI sequence number 02322. DFoNP         contains Source Node Number 02304 and a DFoNP Sequence Number         02305 which is different from STPI sequence number. Expanded         view of STPI[1] is shown.     -   xii) FIG. 2L illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. STPI         contains layer 2 02354 (including destination node address for         routing) and layer 3 information 02353 and part of layer 5/6/7         02357 protocol information. The DFoNP contains minimal layer 2         Header 02331 mandated by datalink layer of the subnet, layer 4         02333 and part of layer 5/6/7 02334 protocol information. The         DFoNP contains control data 02335 such as requests to open a         file in addition to data 02335. Frame Type in the frame gives         the type of frame, DFoNP 02332, STPI 02342, etc. The STPI[1]         02344 is the only STPI 02343 in the STPI Frame. STPI contains         the node number 02355 and buffer address 02356 in the node to         the location of the corresponding DFoNP. When DFoNP is         transmitted to the next node, the node number 02355 and buffer         address 02356 in the corresponding STPI are updated. STPI also         contains the Source Node Number 02351 and STPI sequence number         02352. The layer 2 header 02341 of the STPI frame contains next         hop node address. Expanded view of the STPI[1] 02344 is shown.     -   xiii) FIG. 2M illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. STPI         contains layer 2 02386 (including destination node identifier         used for routing), layer 3 02385 and layers 5/6/7 02387 protocol         information. The DFoNP contains layers 2 02361, layer 3 02363         and layer 4 02364 protocol information. Frame Type in the frame         gives the type of frame, DFoNP 02362, STPI 02372, etc. STPI         frame contains two STPIs 02373 and expanded view of the 2nd STPI         (STPI[2]) 02376 is shown. The STPI frame contains offsets 02374         to all STPIs in the frame. The network in this example supports         more than one length for STPIs. STPI[1] offset 02374 gives the         location of the first STPI (STPI[1] 02375) in the STPI frame.         STPI[2] offset 02374 gives the location of the second STPI in         the STPI frame. Offsets in this example are with respect to         beginning of the frame. STPI contains the node number 02381 and         buffer address 02382 in the node to the location of the         corresponding DFoNP. When DFoNP is transmitted to the next node,         the node number 02381 and buffer address 02382 in STPI are         updated. STPI also contains Source Node Number 02383 and STPI         sequence number 02384. The layer 2 header 02371 of the STPI         frame contains next hop node address.     -   xiv) FIG. 2N illustrates example formats for DFoNP, the         corresponding STPI and an STPI frame which contain STPIs. STPI         contains layer 2 02415 (including destination node identifier         used for routing) protocol information. The DFoNP contains layer         2 02391, layers 3 02394 and layer 4 02394 protocol information.         Frame Type in the frame gives the type of frame, Read Completion         02392 for DFoNP frame and Write 02402 for STPI frame. The STPI         Frame contains the length of write 02403 (which is the length of         STPI[1] 02404 and STPI[2] 02405) and address 02403 for the         write. DFoNP contains Read Requester ID 02393 (Identifier) and a         tag 02393 to identify the read request. DFoNP also contains         address 02393 from which the layer 3/4 headers and the data         02395 is read and the length 02393 of the read. The STPI Frame         contains two STPIs and expanded view of the 2nd STPI (STPI[2])         02405 is shown. STPI contains the node number 02411 and buffer         address 02412 in the node to the location of the corresponding         DFoNP and the length of the DFoNP 02416. These information are         used to read the corresponding DFoNP. When DFoNP is transmitted         to the next node, the node number 02411 and buffer address 02412         in STPI are updated. STPI also contains Source Node Number         02413, STPI Sequence Number 02414 and Miscellaneous 02416         information. The layer 2 header 02401 of the STPI frame contains         next hop node address.

Below five options for transferring STPI and the corresponding DFoNP from one node to another, are described. One of the first 4 methods can be used for transferring STPI and the corresponding DFoNP from the originating node or a switch to another switch or end node. The fifth method can be used for transferring STPI and the corresponding DFoNP to a destination end node:

-   -   i) FIG. 3A, FIG. 3B, FIG. 3C, FIG. 3D and FIG. 3E illustrate one         of the options that could be used in a given network for         transmitting STPI and DFoNP to the next hop node. In this option         a switch/node responds to Read-STPI request by transmitting         STPIs. The switch/node receiving STPIs sends Read-DFoNP requests         using the information contained in STPIs to fetch the         corresponding DFoNPs. A frame containing a Read-STPI request is         called Read-STPI Frame. A frame containing Read-DFoNP requests         is called Read-DFoNP Frame. In FIG. 3A, Switch/Node A 03001         contains an STPI 03003 and the corresponding DFoNP 03004 to be         transmitted to the Switch/Node B 03002. In FIG. 3A, the         Switch/Node B transmits Read-STPI Frame 03005 to the Switch/Node         A giving the maximum number of STPIs that can be transmitted.         The maximum number of STPIs 03005 are 5 in the example. In FIG.         3B, the Switch/Node A responds by sending an STPI frame 03011         containing the STPI 03003 (the STPI frame in this example can         contain up to 5 STPIs). In FIG. 3C, the Switch/Node B decides to         fetch the DFoNP corresponding to the STPI 03003 and sends         Read-DFoNP Frame 03021 to the Switch/Node A containing the         Read-DFoNP request for the DFoNP 03004. The Read-DFoNP request         contains the location (a location could be a buffer address or         an offset in a buffer or an index or a combination of addresses,         offsets or indexes) of the DFoNP 03004 in the Switch/Node A. The         location of the DFoNP to be used in Read-DFoNP request will be         present or can be derived from the contents of the corresponding         STPI 03003. In FIG. 3D, the Switch/Node A responds to the         Read-DFoNP request for the DFoNP by sending the DFoNP 03004. In         FIG. 3E, the STPI 03003 is updated with the identifier of the         Switch/Node B and the location of the DFoNP 03004 in the         Switch/Node B.     -   ii) FIG. 4A, FIG. 4B, FIG. 4C and FIG. 4D illustrate another         option for transmitting STPI and the corresponding DFoNP to the         next hop node. In this option, a switch/node transmits STPIs         followed by DFoNPs corresponding to the STPIs transmitted. In         FIG. 4A Switch/Node A 04001 contains an STPI 04003 and the         corresponding DFoNP 04004 to be transmitted to the Destination         Node B 04002. In FIG. 4B, the Switch/Node A transmits an STPI         Frame 04011 containing the STPI 04003 to the Switch/Node B. In         FIG. 4C, the Switch/Node A transmits the DFoNP 04004 to the         Switch/Node B. In FIG. 4D, the Switch/Node B updates the STPI         04003 with the location of the DFoNP 04004 in the Switch/Node B.     -   iii) FIG. 5A, FIG. 5B, FIG. 5C, FIG. 5D and FIG. 5E illustrate         another option for transmitting STPI and the corresponding DFoNP         to the next hop node. In this option a switch/node transmits         STPIs and the switch/node receiving STPIs sends Read-DFoNP         requests using information contained in STPIs to fetch the         corresponding DFoNPs. In FIG. 5A Switch/Node A 05001 contains an         STPI 05003 and the corresponding DFoNP 05004 to be transmitted         to the Switch/Node B 05002. In FIG. 5B Switch/Node A transmits a         frame 05011 containing the STPI to the Switch/Node B. In FIG.         5C, the Switch/Node B decides to fetch the DFoNP corresponding         to the STPI and sends Read-DFoNP Frame 05021 to the Switch/Node         A containing DFoNP request for the DFoNP 05004. The DFoNP         request contains the location of the DFoNP 05004. The location         of the DFoNP used in the Read-DFoNP request will be present or         can be derived from the contents of the corresponding STPI         05003. In FIG. 5D, the Switch/Node A responds to the Read-DFoNP         request by transmitting the DFoNP 05004. In FIG. 5E, the STPI         05003 is updated with identifier of Switch/Node B and the         location of the corresponding DFoNP 05004 in the Switch/Node B.     -   iv) FIG. 6A, FIG. 6B, FIG. 6C and FIG. 6D illustrate another         option for transmitting STPI and DFoNP to the next hop node. In         this option a switch/node responds to Read-STPI request by         transmitting STPIs followed by the corresponding DFoNPs. In FIG.         6A Switch/Node A 06001 contains an STPI 06003 and the         corresponding DFoNP 06004 to be transmitted to the Switch/Node B         06002. The Switch/Node B transmits Read-STPI Frame 06005 to the         Switch/Node A giving the maximum number of STPIs that can be         transmitted. The maximum number of STPIs 06005 is 0 in the         example indicating that all STPIs can be transmitted. In FIG.         6B, the Switch/Node A responds by sending an STPI frame 06011         containing all STPIs to be transmitted to the Switch/Node B. In         FIG. 6C, the Switch/Node A transmits the DFoNP 06004         corresponding to the STPI to the Switch/Node B. In FIG. 6D, the         STPI 06003 is updated with identifier of the Switch/Node B and         the location of the corresponding DFoNP 06004 in the Switch/Node         B.     -   v) FIG. 7A, FIG. 7B, FIG. 7C, and FIG. 7D illustrate an option         which can be used for transmitting DFoNP and optionally the         corresponding STPI from a switch/node to a destination node: In         this option DFoNP is transmitted to the destination node and         then optionally, the corresponding STPI is transmitted. In FIG.         7A, Switch/Node A 07001 contains an STPI 07003 and the         corresponding DFoNP 07004 to be transmitted to the Destination         End Node B 07002. In FIG. 7B, Switch/Node A transmits the DFoNP         07004 to the Destination End Node B and updates the STPI 07003         with the location (DMA address) of the DFoNP in the Destination         End Node B. In FIG. 7C, Switch/Node A transmits the STPI in an         STPI frame 07021 to the Destination End Node B. In FIG. 7D, both         STPI 07003 and DFoNP 07004 are received by End Node B.

A switch can employ one of the STPI and DFoNP transfer options (strategies) listed above, for each port. Both ports on a point-to-point link must agree to the same frame transmitting option. All ports on a link or bus must follow the same frame transmitting option. Preferably, a network employs only one of the four STPI/DFoNP transfer options listed in FIG. 3A to FIG. 3E, FIG. 4A to FIG. 4D, FIG. 5A to FIG. 5E, FIG. 6A to FIG. 6D. Preferably, a network also employs the STPI/DFoNP transfer option listed in FIG. 7A to FIG. 7D. For the option corresponding to FIG. 7A to FIG. 7D, updating STPI with address (location) of DFoNP in the end node is optional.

If DFoNPs do not contain information (such as originating node identifier, DFoNP identifier, DFoNP address in previous node, etc.) that allow a DFoNP to be mapped to the corresponding STPI, then the DFoNPs must be transmitted in the same order as requested in Read-DFoNP frame/s with design options listed in FIG. 3A to FIG. 3E and FIG. 5A to FIG. 5E. With design options listed in FIG. 4A to FIG. 4D and FIG. 6A to FIG. 6D, if DFoNPs do not contain information that allow the DFoNP to be mapped to the corresponding STPI, DFoNPs must be transmitted in the same order as the corresponding STPIs are transmitted. This will allow switches to identify STPI corresponding to an DFoNP that is received.

There are a very large number of design options with network component designers with respect to the format of Read-STPI request and Read-STPI Frames containing Read-STPI request. FIG. 8A, FIG. 8B, FIG. 8C and FIG. 8D illustrate some examples of different formats in which the Read-STPI Frames can be created adhering to this invention. Preferably a given network employs only one format (design option) for Read-STPI request to keep the design of switches and end nodes simple.

-   -   i) FIG. 8A illustrates a Read-STPI frame with Frame Type         “Read-STPI” 08001 and “Number of STPIs” 08002 set to 3. The         frame also contains Miscellaneous 08003 field.     -   ii) FIG. 8B illustrates a Read-STPI frame in a network where         explicit frame type specification is not required. The frame         specifies an address 08011 for read (the location of the STPIs)         in the node receiving the Read-STPI Frame. The frame also         provides the length 08012 for read. The address where STPIs are         stored can be dynamically configured on the switch for each         node/switch it is connected to.     -   iii) FIG. 8C illustrates a Read-STPI frame in a network without         layer 1 headers or trailers. Frame Type 08021 is “Read-STPI”.         The “Number of STPIs” 08022 is 0 indicating permission to         transmit an STPI Frame with as many STPIs for the node         transmitting Read-STPI Frame as possible, from the node         receiving the Read-STPI Frame. The frame also contains a         Miscellaneous 08023 field.     -   iv) FIG. 8D illustrates a Read-STPI frame in a network without         layer 1 headers or trailers. Layer 2 header 08031 contains Frame         Type (Read-STPI). The “Number of STPIs” 08032 is −1 indicating         permission to transmit all STPIs for the node transmitting         Read-STPI Frame, from the node receiving the Read-STPI Frame.

A Read-DFoNP Frame contains one or more Read-DFoNP requests and each Read-DFoNP request contains the location of the requested DFoNP. There are a very large number of design options with network component designers with respect to the format of Read-DFoNP requests and Read-DFoNP Frames containing Read-DFoNP requests. FIG. 9A, FIG. 9B, FIG. 9C and FIG. 9D illustrate some examples of different formats in which the Read-DFoNP Frame can be created adhering to this invention. Preferably, a given network employs only one format (design option) for Read-DFoNP request to keep the design of switches and end nodes simple.

-   -   i) FIG. 9A, illustrates a Read-DFoNP frame with Frame Type 09001         “Read-DFoNP” and “Number of Read-DFoNP requests” 09002 set to 2.         The DFoNP[1] 09003 and DFoNP[2] 09004 buffer addresses provide         the location of the DFoNPs in the node receiving the Read-DFoNP         Frame. The frame also contains Miscellaneous 09005 field.     -   ii) FIG. 9B illustrates a Read-DFoNP frame in a network where         explicit frame type specification is not required. Frame         specifies an address 09011 for read (the location of the DFoNP)         in the node receiving the Read-DFoNP Frame. The frame also         provides the length 09012 for read.     -   iii) FIG. 9C illustrates Read-DFoNP frame in a network without         layer 1 headers or trailers. Frame Type 09021 is “Read-DFoNP”,         the “Number of Read-DFoNP requests” 09022 is 3. Each Read-DFoNP         request contains a buffer address and an offset. The DFoNP[1]         09023, DFoNP[2] 09024 and DFoNP[3] 09025 buffer addresses and         offsets provide the location of the DFoNPs in the node receiving         the Read-DFoNP Frame.     -   iv) FIG. 9D illustrates a Read-DFoNP frame in a network without         layer 1 headers or trailers. Frame Type (Read-DFoNP) is         contained in layer 2 header 09031. Only one Read-DFoNP request         09032 is allowed in the frame and the Read-DFoNP request gives         the index of the DFoNP to be read.

Optionally, a switch or node can send the number of STPIs available for transmission to the next hop node or switch. There are a very large number of design options with network component designers with respect to the format of Number-of-STPIs message and Number-of-STPIs Frames containing Number-of-STPIs message. FIG. 10A, FIG. 10B, FIG. 10C and FIG. 10D illustrate some examples of different formats in which the Number-of-STPIs Frame can be created adhering to this invention. Preferably a given network employs only one format for Number-of-STPI message to keep the design of switches and end nodes simple.

-   -   i) FIG. 10A, illustrates a Number-of-STPIs frame with Frame Type         10001 “Number-of-STPIs” and “Number of STPIs” 10002 set to 3.         The frame also contains a Miscellaneous 10003 field.     -   ii) FIG. 10B illustrates Number-of-STPIs frame in a network         where explicit frame type specification is not required. Frame         specifies an address 10011 to the location where value of Number         of STPIs will be written and the length 10012 of the field to be         written. The next field contains data (Number of STPIs) 10013         for the write, which is 2.     -   iii) FIG. 10C illustrates Number-of-STPIs frame in a network         without layer 1 headers or trailers. Frame Type 10021 is         “Number-of-STPIs”. The “Number of STPIs” 10022 is 3. The frame         also contains a Miscellaneous 10023 field.     -   iv) FIG. 10D illustrates a Number-of-STPIs frame in a network         without layer 1 headers or trailers. Layer 2 header 10031         contains Frame Type (Number-of-STPIs). The “Number of STPIs”         10032 is 1.

The network described in this invention can be connected to an I/O card (in a server or embedded system) or to a PCI bus.

-   -   i) The switch corresponding to this invention can be connected         to an Ethernet card.         -   a) A recommended frame format for use with Ethernet is as             follows:             -   1) Ethernet header contains destination MAC: The network                 can use next hop MAC address in the                 STPI/DFoNP/Read-STPI/Read-DFoNP/Number-of-STPIs frame.             -   2) Ethernet header contains source MAC address: A DFoNP                 frame can contain the MAC address of the originating                 node in this field. All other types of frames (STPI,                 Read-STPI, Read-DFoNP, Number-of-STPI) can contain MAC                 address of the node transmitting the frame in this                 field.             -   3) The Ethernet header contains length field as per                 Ethernet Protocol standard.             -   4) The first byte of the data field contains the                 “Frame-Type”: one bit each for STPI, DFoNP, Read-STPI,                 Read-DFoNP and Number-of-STPIs.             -   5) Each STPI will contain the final destination MAC                 address. Optionally, each STPI can also contain source                 MAC address of the originating node of the STPI.             -   6) The formats specified examples such as FIG. 2A, FIG.                 2C etc., can be used with Ethernet.             -   7) The Ethernet trailer contains FCS for the frame.         -   b) FIG. 11A illustrates an example of DFoNP and STPI frames             which can be used with Ethernet. FIG. 11B illustrates             Read-DFoNP frame which can be used with Ethernet.             -   1) Destination MAC address 11001 in DFoNP frame is the                 MAC address corresponding to the port or node (next hop                 node) receiving the frame. If switches are designed to                 ignore Destination MAC address in a DFoNP frame, the                 final destination node MAC address could be used in the                 Destination MAC address field.             -   2) Source MAC address 11002 in the DFoNP frame is the                 MAC address of the node that created the DFoNP.             -   3) The length field 11003 provides the length as per                 Ethernet Protocol standard.             -   4) The first field in the data portion of Ethernet Frame                 is Frame Type 11004 and Frame Type of DFoNP frame is                 DFoNP (DFoNP bit is set).             -   5) The DFoNP contains layer 3 11005, layer 4 11006                 protocol information and data 11007.             -   6) Destination MAC address 11011 in the STPI frame is                 the MAC address corresponding to the port or node (next                 hop node) receiving the frame.             -   7) Source MAC address 11012 in the STPI frame is the MAC                 address corresponding to the port transmitting the                 frame.             -   8) The length field 11013 provides the length as per                 Ethernet Protocol standard.             -   9) The first field in the data portion of the Ethernet                 Frame is Frame Type 11014 and Frame Type of STPI frame                 is STPI (STPI bit is set).             -   10) The STPI frame in this example contains 2 STPIs                 11015.             -   11) Expanded view of the second STPI 11016 is shown.             -   12) Each STPI contains the Final Destination MAC address                 11021 for the STPI and the corresponding DFoNP. Switches                 can use this address for routing.             -   13) The STPI contains the Source MAC Address 11022 of                 the Ethernet port through which the STPI entered the                 Ethernet LAN.             -   14) STPI contains “Destination STPI Address” 11023 which                 is the address to be used for RDMA Writing the STPI in                 the destination node.             -   15) STPI contains “Destination DFoNP Address” 11024                 which is the address to be used for RDMA Writing the                 corresponding DFoNP in the destination node.             -   16) The STPI contains the MAC address of the node                 containing DFoNP 11025, buffer address 11026 of the                 DFoNP in this node and length 11026 of the DFoNP. These                 fields are used to create Read-DFoNP request.             -   17) After an STPI an STPI frame is received, the next                 hop node can initiate read for the corresponding DFoNP.                 FIG. 11B illustrates a Read-DFoNP frame containing 3                 Read-DFoNP requests.             -   18) The destination MAC address 11031 in the Read-DFoNP                 frame is the “DFoNP Current Node MAC address” 11025 from                 the STPI.             -   19) The source MAC address 11032 in the Read-DFoNP frame                 is the MAC address corresponding to the port                 transmitting the Read-DFoNP Frame.             -   20) The length field 11033 provides the length as per                 Ethernet Protocol standard.             -   21) The first field in the data portion of the Ethernet                 Frame is Frame Type 11034 and Frame Type of Read-DFoNP                 frame is “Read-DFoNP” (“Read-DFoNP” bit is set).             -   22) The Number of DFoNPs 11035 being requested from the                 node receiving Read-DFoNP frame is 3 in this example.             -   23) The DFoNP buffer address 11036 and the length 11036                 of DFoNP in Read-STPI frame are from DFoNP Current                 Buffer Address 11026 and DFoNP Length 11026 fields in                 STPI.     -   ii) If the switch corresponding to this invention is connected         to a PCI bus, it behaves like an end node. The switch will use         PCI transactions to communicate with the server.         -   a) The host (in turn the PCI root bridge) can use PCI memory             write transaction to transfer STPIs to a switch             corresponding to this invention OR the switch can use PCI             memory read transaction to read STPIs. The host can use PCI             memory write transaction to write the address of the memory             location holding STPIs which the switch can use for PCI             Memory Read transaction.         -   b) The switch can use PCI read transaction to read each             DFoNP using the buffer address contained in the             corresponding STPI.         -   c) The host (in turn the PCI root bridge) can optionally use             PCI write transaction to write the number of STPIs to a             switch corresponding to this invention.         -   d) The switch can use PCI memory write to write DFoNPs and             STPIs to the memory of the destination node.         -   e) FIG. 12A, FIG. 12B, FIG. 12C and FIG. 12D illustrate an             example of transaction formats which can be used within PCI             Express™ (PCI Express™ is a trade mark of PCI-SIG)             transactions for transferring STPIs and DFoNPs from root             bridge to a switch corresponding to this invention and vice             versa.             -   1) Example in FIG. 12A illustrates format of PCI Express                 Read Completion containing DFoNP, from a root bridge in                 response to a Memory Read request from a switch. The                 first field of PCI Express Read Completion data provides                 the Frame Type 12001 which is DFoNP. The rest of the                 Read Completion data is layer 3/4 protocol information                 12002 and Data 12003 being transmitted to the remote                 node.             -   2) Example in FIG. 12B illustrates format of PCI Express                 Read Completion containing STPIs, from a root bridge in                 response to a Memory Read request from a switch. The                 first field of data provides the Frame Type 12011 which                 is STPI. The second field in data is “Number of STPIs”                 12012 which is 3 followed by three STPIs 12013. Each                 STPI contains “Final Destination Node Identifier” 12021                 which is used by switches for routing, Source Node                 Identifier 12022 which is the identifier of the node                 that created the STPI, “Destination STPI Address” 12023                 to be used for RDMA Writing STPI in the destination,                 “Destination DFoNP Address” 12024 to be used for RDMA                 Writing the corresponding DFoNP in the destination,                 “DFoNP Current Node ID” 12025, DFoNP Length and DFoNP                 Current Address 12026 to be used for reading DFoNP from                 the node where it is currently stored. The DFoNP Length                 field 12026 is also used for RDMAing DFoNP to the memory                 of the destination node.             -   3) Example in FIG. 12C illustrates a PCI Express Memory                 Write transaction containing DFoNP, from a switch to a                 root bridge. The first field of PCI Express Memory Write                 transaction data provides the Frame Type 12031 which is                 DFoNP. The rest of the Read Completion data is layer 3/4                 information 12032 and Data 12033 that arrived from the                 remote node.             -   4) Example in FIG. 12D illustrates a PCI Express Memory                 Write transaction containing STPIs, from a switch to a                 root bridge. The first field of PCI Express Memory Write                 data provides the Frame Type 12041 which is STPI. The                 second field in the data is “Number of STPIs” 12042                 which is 2 followed by two STPIs 12043. Each STPI                 contains “Final Destination Node Identifier” 12051 which                 is used by switch for routing, Source Node Identifier                 12052 which is the identifier of the node that created                 the STPI, a miscellaneous field 12053, “DFoNP Current                 Node Identifier” 12054, DFoNP Current Buffer Address                 12055 and DFoNP Length 12055 to be used for reading                 DFoNP from the node where it is currently stored. The                 DFoNP Length field 12055 is also used for doing PCI                 Express Memory Write transaction to the root bridge                 (DMAing DFoNP to the memory of the destination node).                 The DFoNP and STPI are DMAed into read buffers provided                 by the destination node.

When destination address contained in an STPI is a Multi-cast and Broadcast address, both STPI and DFoNP are transmitted to all next hop nodes identified by the Multi-cast or Broadcast address.

When STPI or DFoNP frames are corrupted or lost, switches and nodes may employ retransmission of the corrupted or lost frame. The retransmission policy and error recovery are link (example PCI) and vendor specific.

Some networks allow more than one type of content to be present in the same frame. The types of contents are STPI, DFoNP, Read-STPI request, Read-DFoNP request and Number-of-STPIs message.

-   -   i) FIG. 13A illustrates a frame containing both Number-of-STPIs         message and Read-DFoNP requests. The Frame Type 13001 is a         bit-OR of “Number-of-STPIs” and “Read-DFoNP”. The “Number of         STPIs” 13002 is 5 indicating that there are 5 STPIs available to         be transmitted to the receiving node. The “Number of DFoNPs”         13003 is 3 and the receiving node is expected to respond to the         request by transmitting the three DFoNPs requested.     -   ii) FIG. 13B illustrates a frame containing both Read-STPI         request and Read-DFoNP requests. The Frame Type 13011 is a         bit-OR of “Read-STPI” and “Read-DFoNP”. The “Number of STPIs”         field 13012 is 2 and the “Number of DFoNPs” field 13013 is 3.         The node receiving the frame is expected to respond with two         STPIs and the three requested DFoNPs.

FIG. 14A and FIG. 14B illustrate an example of reading DFoNPs in a different order compared to the order in which STPIs are received. In FIG. 14A, Switch A 14001 has 3 DFoNPs 14004 to be transmitted to Switch B 14002. The Switch A forwards 3 STPIs corresponding to the DFoNPs in an STPI frame 14003 to Switch B. The Switch B has 10 STPIs in its queue 14006 for its link to node D. The switch B has no STPIs in its queue 14005 for its link to node C. In FIG. 14B, the switch identifies that STPI[1] and STPI[2] received are for node D and adds STPI[1] and STPI[2] to the queue 14006 for the node D. The Switch B delays reading DFoNP[1] and DFoNP[2] since there are a large of STPIs already queued for the node D. The Switch B identifies that STPI[3] received is for the node C and queues STPI[3] to the queue 14005 for the node C. The Switch B sends Read-DFoNP Frame 14013 to the Switch A with DFoNP[3] address.

If STPI contains a priority or QoS field, a switch can use it for controlling the order in which DFoNPs are read. Similarly, a priority or QoS field in STPI or DFoNP could be used by switches or nodes to control the order in which STPIs are transmitted to the next node.

A network corresponding to this invention could be used to connect a server or servers to storage devices (such as disks, disk arrays, JBODs, Storage Tapes, DVD drives etc.). iSCSI and iSER (iSCSI Extensions for RDMA) are examples in which SCSI commands and SCSI data are transmitted using networks technologies used for server interconnect.

ADVANTAGES

A switch can delay receiving DFoNP for paths which are already congested.

A switch can read DFoNP corresponding to a lightly loaded link ahead of other DFoNPs and transmit STPI and DFoNP more quickly to the lightly loaded link improving link efficiency.

A switch can delay reading DFoNPs based on QoS or priority field in STPI.

A switch can optimize switch resources, memory and frame/packet queues as congestions are minimized by delaying DFoNPs for ports which are already congested.

The switch can ensure higher throughput on all links by rearranging order in which DFoNPs are read. 

What is claimed is:
 1. A method implemented in a first network switch used for forwarding data link frames, wherein said first network switch is used for interconnecting network nodes in a network, said method comprising: a) receiving a first data link frame; b) receiving at least one second data link frame; c) receiving a first request, wherein said first request is received in a third data link frame, wherein said third data link frame does not contain network packet, wherein said third data link frame does not contain data; and d) responding to said first request by transmitting said at least one second data link frame to a second network switch before transmitting said first data link frame to said second network switch, wherein said first data link frame and said at least one second data link frame are transmitted from a network port in said first network switch to said second network switch.
 2. The method of claim 1, wherein said first data link frame is to be transmitted out of a first queue in said second network switch, wherein said at least one second data link frame is to be transmitted out of a second queue in said second network switch.
 3. The method of claim 2, wherein said first request is sent from said second network switch.
 4. The method of claim 3, wherein said first request is not received by said second network switch.
 5. The method of claim 3, wherein said second network switch transmitting said first request to said first network switch to lower congestion in the network.
 6. The method of claim 3, wherein network load on said first queue is more than network load on said second queue when said first request is sent from said second network switch.
 7. The method of claim 2, wherein said first request is used to lower congestion in the network.
 8. A method implemented in a first network switch used for forwarding data link frames, wherein said first network switch is used for interconnecting network nodes in a network, said method comprising: a) receiving a first data link frame; b) receiving at least one second data link frame; c) receiving a third data link frame from a second network switch, wherein said third data link frame does not contain layer 3 header, wherein said third data link frame does not contain data; and d) responding to said third data link frame by transmitting said at least one second data link frame to said second network switch before transmitting said first data link frame to said second network switch, wherein said first data link frame and said at least one second data link frame are transmitted from a network port in said first network switch to said second network switch, wherein said first data link frame is to be transmitted out of a first queue in said second network switch, wherein said at least one second data link frame is to be transmitted out of a second queue in said second network switch, wherein network load on said first queue is more than network load on said second queue when said third data link frame is sent from said second network switch.
 9. The method of claim 8, wherein said second network switch transmitting said third data link frame to said first network switch to lower congestion in the network.
 10. The method of claim 9, wherein said third data link frame is not received by said second network switch.
 11. A first network switch enabled for forwarding data link frames, wherein the first network switch is configured for interconnecting to other network nodes in a local area network, the first network switch further configured to: a) receive a first data link frame; b) receive at least one second data link frame; c) receive a first request in a third data link frame from a second network switch, wherein the third data link frame does not contain data, wherein the third data link frame does not contain network packet; and d) respond to the first request by transmitting the at least one second data link frame to the second network switch before transmitting the first data link frame to the second network switch, wherein the first data link frame and the at least one second data link frame are transmitted from a network port in the first network switch to the second network switch in an order different from the order in which the first data link frame and the at least one second data link frame were received by the first network switch.
 12. The local area network of claim 11, wherein the second network switch is configured to: forward the first data link frame using a first queue in the second network switch and forward the at least one second data link frame using a second queue in the second network switch, wherein network load on the first queue is more than the network load on the second queue in the second network switch when the first request is sent from the second network switch to the first network switch.
 13. The first network switch of claim 12, wherein the first request received by the first network switch is used to lower congestion in the network.
 14. A system in a network comprising a plurality of interconnected network nodes, wherein the network comprises a first network switch and a second network switch, wherein the first network switch and the second network switch are configured for interconnecting network nodes in the network and for forwarding data link frames, the first network switch is configured to: a) receive a first data link frame; b) receive at least one second data link frame; c) receive a third data link frame from the second network switch, wherein the third data link frame does not contain data, wherein the third data link frame does not contain network layer header; and d) respond to the third data link frame by transmitting the at least one second data link frame to the second network switch before transmitting the first data link frame to the second network switch, wherein a first queue in the second network switch is configured to be used for forwarding the first data link frame, wherein a second queue in the second network switch is configured to be used for forwarding the at least one second data link frame, wherein the first data link frame and the at least one second data link frame are configured to be transmitted from a network port in the first network switch to the second network switch.
 15. The system of claim 14, wherein network load on the first queue in the second network switch is more than network load on the second queue in the second network switch when the first request is sent from the second network switch.
 16. The system of claim 15, wherein the first request received by the first network switch is used to lower congestion in the network.
 17. A system configured for lowering congestion in a network, the system comprising: a) a first network switch configured to interconnect a plurality of network nodes in the network and to forward data link frames; the first network switch configured to receive a first data link frame and at least one second datalink frame; the first network switch configured to receive a first request in a third data link frame from a second network switch, wherein the third data link frame does not contain data, wherein the third data link frame does not contain network packet; and the first network switch responding to the first request by sending the at least one second data link frame before sending the first data link frame to the second network switch, wherein the first data link frame and the at least one second data link frame are transmitted from a network port in the first network switch to the second network switch, wherein the response to the first request causes reordering of data link frames sent from the first network switch to the second network switch; and b) the second network switch configured to interconnect a plurality of network nodes in the network and to forward data link frames; the second network switch configured to forward the first data link frame using a first queue in the second network switch and to forward the at least one second data link frame using a second queue in the second network switch, wherein the third data link frame is sent when network load on the first queue is higher than network load on the second queue.
 18. A system comprising multiple interconnected network nodes, the system comprising a first network switch and a second network switch configured for interconnecting network nodes in a network and for forwarding data link frames; and the system configured to implement a method for congestion reduction in the network, the method comprising: a) the first network switch receiving a first data link frame; b) the first network switch receiving at least one second data link frame; c) the first network switch receiving a third data link frame, wherein the third data link frame does not contain data; wherein the third data link frame does not contain network layer header; and d) the first network switch responding to the third data link frame by transmitting the at least one second data link frame to the second network switch before transmitting by the first network switch the first data link frame to the second network switch, wherein the first data link frame and the at least one second data link frame are transmitted from a network port in the first network switch to the second network switch; e) the second network switch configured to use a first queue for forwarding the first data link frame; f) the second network switch configured to use a second queue for forwarding the at least one second data link frame; and g) the second network switch configured to send the third data link frame when the first queue is more loaded compared to the second queue.
 19. The system of claim 18, wherein the use of the third data link frame and the first network switch being configured to respond to the third data link frame by reordering the datalink frames enabling the system to react to a congestion at the second network switch.
 20. The system of claim 19, wherein the reordering of the data link frames is by transmitting the first datalink frame and the at least one second data link frame from the network port in the first network switch in an order different from the order in which they were received by the first network switch. 